1. Technical Field
This invention relates to vehicle safety and, more particularly, to a reinforcing structure for a vehicle door.
2. Discussion
Conventional vehicle doors are generally equipped with a rigid intrusion beam in order to limit penetration resulting from a side impact. This practice has proven successful in meeting prior side impact Federal Motor Vehicle Safety Standards which required a quasi-static test. In the prior test, a pole is slowly forced into the side of a stationary vehicle and the vehicle door is required to meet minimum specified force-deflection characteristics.
Extensive testing done with an anthropomorphic test device (ATD), otherwise known as a crash dummy, has indicated that the prior standard was not representative of actual side impact collisions, and further that compliance with the current standard is not necessarily sufficient to protect the occupant. During a side impact collision, as with other collisions, two impacts occur. When a first car, the striking car, collides with a second car, the struck car, a first impact occurs immediately. Milliseconds later, the second impact occurs in which the occupant and the interior of the vehicle door collide. It is this second impact which directly inflicts injury upon the occupant.
As a result of the prior standard's inability to replicate the results of a side impact collision, an amendment to the side impact standards, adopted Nov. 2, 1990, requires a dynamic test. In this test, a moving barrier, simulating a striking vehicle, would impact a stationary vehicle at a speed of 33.5 miles per hour. Thoracic and pelvic accelerations taken from the ATD would be required to not exceed specified maximums. To meet the requirements of the new amendment, which is scheduled to be gradually implemented begin in model year 1994, vehicle doors must increase their energy absorption capacities.
Several devices used to reinforce vehicle doors from the impact of a side collision are known. U.S. Pat. No. 3,868,141 to Johnson relates to elongated members disposed vertically between the exterior panels of a vehicle door. U.S. Pat. No. 3,700,076 to Forsting et al. relates to an energy absorbing band anchored on the door end walls. U.S. Pat. No. 4,328,642, relates to a stamped intrusion beam attached to the inner door frame of a vehicle.
None of the above-discussed devices is without its problems. While these known devices may have proven satisfactory for applications in the past, their efficiency, cost, methods of manufacture, and energy absorption capacity can be improved.